<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<button id="btn">111</button>
		<script>
			var  btn=document.getElementById("btn");
			btn.onclick=function(){
				console.log(this);//触发事件的元素
			}
		</script>
	</body>
</html>
